Experiencing intermittent less than 1ppm iron.
Adding Katalox Light did not solve problem.
Recently converted Katalox Light to Pot Perm regeneration, but still experiencing occasional  less than 1 ppm iron.
No obvious problems.
I'll have to dedicate most of a day to trying to solve this problem, again.

One cubic foot of Katalox light with 10x44 vortech tank with 5810 Fleck valve installed yesterday.
Brine draw version of the 5810 valve was delivered with piston for brine draw. As the system was installed before I discovered this the solution was to set BD to one and BF to zero and plug brine port as possible. Brine port plug to be delivered.
Tank was installed after calcite and before MTM. All tanks were manually regenerated. Water looks clear. Will need to monitor seals and spacers for chlorine degradation (calcite, Katalox, MTM, and carbon tanks could all be at risk).

Manually regenerated all tanks last night and today water was B in clarity/color. I have no ideas.

Water B+ this morning. Not ideal. Manually regenerating all tanks.

Situation promising.
After two weeks of poor outcomes water condition today looks in the "A" range.
Several variables may have contributed to our problems, most significantly being daylight savings and regeneration scheduling overlap.
a) All cycle times should be reviewed.
b) backwash lines should be monitored for activity
c) seals and spacers on tanks one through three should be replaced periodically
d) salt usage should be monitored, currently on a low flow restrictor

Regeneration Times RT changed
It is likely wife was taking showers before MTM tank finished cycling.
Also softener time was overlapping with calcite/corosex time.
Are our current water problems solved?

Updated start times:
#1 12:01 (calcite/corosex)
#2 12:45 (MTM)
#3 2:45 (carbon)
#4 3:15 (resin)

Master programming settings:
#1
VT dF2b
CT Fd
C 24
H 30
RS rc
RC 150
DO 5
RT 2:45

#2
VT dF2b
CT Fd
C 35
H 20
RS rc
RC 0
DO 14
RT 3:15

#3
VT Fltr
CT tc
C -
H -
RS -
RC -
DO 7
RT 12:01

#4
VT dF2b
CT Fd
C 24
H 20
RS rc
RC 150
DO 14
RT 12:45

March 2017 status

I have at least 10ppm iron. Our pump generates about 8 gpm.

All my tanks are 10x44 with Fleck 7000 valves with upper baskets.

For several months our water has been perfect.

March 12 our water was a bit brown. 

My MTM tanks seemed to be leaking down the backwash line and replacing the seals, spacer, and piston didn't help.

The leaking valve wasn't a Fleck 7000 so I replaced it with a Fleck 7000 and new MTM media a couple of weeks ago.

Water still brown.

Replinished through dome port calcite/corosex (did not clean tank) 1cf.

Replaced Centaur Carbon 1cf.

Water still brown.

Replaced fine mesh resin 1.25 cf.

Here are my settings:

All tanks are 10x44 with Fleck 7000 valves.

Chlorine injection before the tanks.

Calcite/corosex (1cf total with ratio of about 5 calcite to 1 corosex)

B1:10

B2:3

RR:8

gallons available after backwash 650

MTM

B1:10

BD:60

B2:5

RR:10

BF:12

gallons available after regeneration 1050

Centaur Carbon

BW:10

RR:10

days to next backwash 7

Fine mesh resin

NOTE: Brine Line Flow Control .25 BLFC Button

B1:10

BD:60

B2:5

RR:10

BF:24

gallons available after regeneration 1050

Recently corrected water softener plumbing (resin could be fouled).
Replenished calcite and corosex.
Replaced MTM media.
Replaced Fleck 7000 valve on MTM tank as the old one continued to leak and I think it was due to gear wear rather than seals/spacers.
Replaced Centaur Carbon.
Surprised to find that carbon seemed fouled after six months of use.
Will investigate carbon valve settings.
Flushed retention tanks and found little if any evidence of precipitated iron.
Water again running clear.

ye gods

Water was running brown.
MTM valve leaking through backwash line. Replacing seals spacer and piston did not help.
Seems like the valve was not resetting correctly and manual nudging the gears corrected the problem once. Replaced the valve, tank, and MTM media.
Water continued to run a little brown and determined water softener plumbed backwards.
Some chance softening resin fouled.
Otherwise chlorine injection may be strong.
Seals on calcite and MTM valves should be replaced periodically.
Calcite and corosex should be replenished periodically.