I don't think this is the issue here, but when the Flora-Pride is gone, I would get hold of Seachem's Flourish Comprehensive Supplement. If is the only product known to me that is widely available and contains all essential nutrients [FP has only iron and potassium]. The enriched substrates obviously help, but this has no benefit for floating plants, non-substrate rooted plants (Java Fern, Anubias, moss, etc) and even some stem plants. Flourish Comp may seem expensive, but so little is used that it lasts a long time. In your 29g for instance, as little as 1/2 a teaspoon once a week is the recommended dose.
So back to the original question, it may have been the light. You don't mention the plants that failed, but if stem plants were among them this would be logical as any fast growing plant (such as stem plants) require more light. Red-leaf plants also.
I have never tried the LED light systems, but I have seen them in a local store and they seemed to be providing good light over smallish tanks (shallower than your 29g) so this may be an issue. The Anubias, some swords, and crypts already mentioned should manage. Water Sprite floating will, though this will block some light from reaching the lower plants. But floating plants are so useful and natural to forest fish that I always include them in my tanks.