Meira,

"...are there any other signs to look for?"

This article on Symptoms of Deficiency In Essential Minerals includes several pictures of tomatoes that are deficient in specific nutrients. With a little study, you can "read" the foliage of many different plants to tell which nutrients they need. Sometimes I leave a few small weeds in the garden because they are good "indicators" of what the soil in that spot needs. (Grin.) That's my excuse, and I'm sticking with it.

There is a lot of information in cyberspace on this subject.

MM

It is almost certain that the controlled release fertilizer in the planting mix only contains 3 nutrients, nitrogen, phosphorus and potassium.

There are many more. If these plants will go into the ground then that's one thing, but if they will spend their entire life in a container then you need to add all the nutrients for best results.

Calcium and magnesium are very necessary. Dolomitic lime (will raise pH) will supply both in a good ratio. Commercially prepared, peat based soil-less mixes already have the lime added, but if you made your own mix you would have to add it.

Anyway, to answer your question, plants require fertilizer for best growth once the first true leaves form.

Another tid bit of info: The controlled release fertilizer in commercial potting mixes will release nutrients based upon the temperature of the soil they are in. If the bag says feeds for 3 months this is *always* based upon a soil temp of 70F. Early in the season this will likely be the case (maybe even coolers), but in a container in summer the internal temp will not trail far behind air temps and pots in direct sunlight get even hotter. All this means is that it will feed for much less than the time advertised. Generally I tell people to ignore what the bag says and fertilize as if there was no CRF in the mix.

I just watered my maters with 1/2 strength fish emulsion, they are at 3-4 leaf stage and about to be replanted in larger cups.
When I plant my maters, I trench plant them. Digging a trench 4 inches deep and laying the entire stem, except for 4 leaves out the top. Mater stems will produce roots all along the stem.
While I am making my trench I soak the plants in nEpsom salt water, in the trench I make a mix of ground egg shells, alfalfa meal, super phosphate, kelp meal, if I have blood meal I throw that in. Water well with the Epsom salt water.
I have no problems getting mater 1.5 to 2lbs. I don't have the space anymore for cherry or grape type maters because they get so huge I have to take hedge trimmers to them.

From what I've read (and I've read ALOT) tomatoes should only be fertilized twice before planting, at most.
Ginny

Okay, since they'll live inside always I did add a tomatoe fertilizer to the water that the pots are sitting in. It seems to have done the trick. Along with adding another light. My plants have really grown in a couple of days. Hopefully I'll be throwing tomatoes on my salad soon.