I guess it depends on the type of sprout. You can always try to grow the good ol' dandelion (they sell seeds online). A quick little comparison:
One ounce Alfalfa Sprouts has:
9mg calcium, 19.6 mg phosphorous, 43.4 IU Vitamin A and 1.1 grams protein
One ounce of dandelions has:
52.4 mg calcium, 18.5 mg phosphorous, 2845 IU Vitamin A, and 0.8 g protein
Sources:
http://nutritiondata.self.com/facts/veg ... cts/2302/2http://nutritiondata.self.com/facts/veg ... cts/2441/2Alfalfa sprouts are lower in oxalate than dandelions, but the difference in calcium level is significant, so it is kind of a counterbalance.
Since the key to a good diet of a mature turtle is to avoid over reliance on one or two items, you are on the right track (they can easily become 'addicted; to meat or fish only diets). At 7" it sounds like its time for them to change their acquired taste

neither is real big on vegetables and will hang out under the pellet feeder waiting for it to do its thing rather than explore floating vegetation
Maybe do away with the auto-feeder so they get whatever you give them. If i had a choice between a candy dispenser or veggies, guess what I would choose?
A bit off topic, but
...seem to prefer the little bit of daylight that comes in through the window to their basking and UVB lights.
the light coming from the window may be fun for them, but the window blocks the UVB.