Imps do like some light. Moving them around would help. Maybe a fertilizer that is stronger in the bloom area, for those not blooming so well.

Thanks. What type of fertilizer would be stronger in the bloom area?

I weuld use Osmacote its a pellete type, gives a slow release for several months.

Thanks again. Since there are several types of Osmacote, which do you think would be best for my application? I'm thinking a 13-13-13 or 14-14-14.

Just following up on my original post. Thanks to all you here my impatiens are doing quite well under the porch. Here are my lessons learned (and still learning):

Osmocote (14-14-14) helped immensely
Don't overwater.
All 16 pots cannot be on the same watering schedule.
Some pots receive full sun, partial sun, no sun.
The pots facing east (morning sun) and the west (afternoon sun) are doing the best.
The pots that receive next to no direct sun are the least full and are the smallest, but they are flowering.
The pots on the west side are getting leggy and will require pinching soon.
The west side pots tend to wither a little from the direct last afternoon sun, but they bounce back in the evening.
Only water when needed!

My only question at the moment is when should I apply more Osmocote? It claims to last 4 months, but is this realistic? Thanks.
Dave