No more fertilizing. This looks just fine. The leaves with purple dots just nip them off at the main stem. The plant would do the same to itself only slower. Damaged or too old leaves are not going to be able to do enough photosynthesis to help the plant itself. The purple veins are NORMAL and healthy. Have you grown tomatoes on this window sill and had any tomatoes to harvest? I'd put these plants in 5 gal to 10 gallon pots to go outside. 10 minutes the first couple of days...20 the next couple of days...called acclimation. Need to know where you live and your zone. If you've got iffy nights just keep plants out doors during the day and bring them in at night. To make tomatoes you've got to have lots of light.
Careful with fertilization...use only fertilizer where the nitrogen is the lowest number of the 3 biggies; N P K. 10 -12-12 for instance. You shouldn't fertilize again until you've transplanted into larger containers with fresh potting soil and are taking them outside to acclimate to the out of doors. When acclimated you should be able to plant them directly into the garden soil, don't worry about any additions to the soil...a little fertilizer after they acclimate to their new home. If that is what you want to do.
Too much nitrogen, no tomatoes, just lots of healthy leaves. Too much fertilizer will kill your plants. They look great right now.