Thumb rule in growing indoor plants is - Do not and do not over water your plants. Since the plants are kept away from direct light, photosynthesis will be slower than the plants kept outside. Hence plants require only a lesser quantity of water and fertilizer. One of the major issues for all indoor plants is root rot due to overwatering or any other fungal diseases. If there are any issues shown by your plants check underneath the plants' leaves, if any insects are there. Apply the insecticide if any attack is there. If the plants are weak and yellowish then check the moisture level in the soil. If the soil is completely dry, then give some water. If soil is sufficiently moist, then there may be root rot or fungal infection. Apply fungicide, correct pH level optimum (Add humic acid).
Here you have to keep in mind two things. If it is flowering plants, keep it in direct sunlight. Do not keep in shades. Give a good amount of water during the vegetative growth phase. Give a little stress before the flowering season starts to initiate blooming, and give a good amount of macro and micro nutrients during the flowering season. Do not pour water on the flowers. Most of the plants don’t like watering on the flowers. Give fertilizers with more phosphorus proportion like Bone meal, NPK(18:9(9):18), NPK(20:20:20) etc during flowering season. Give a tiny amount of micronutrients to get better results in flowering. If it is a non-flowering plant, it can be grown in shades as well. Give fertilizers with more proportion of nitrogen and potassium (cow dung, NPK (19:19:19)) etc for vegetative growth.
Find a place where a good amount of direct sunlight is there. Few people will look vastu in planting fruit plants which is well accepted and good practice. The thumb rule is to give ample space for each tree (a fully grown tree). Check how big it will be after 15 years or 20 years. Initial couple of years will be its vegetative growth phase. Give fertilizers which boost its growth (more Nitrogen added). Next phase is its flowering phase. Ideally do not allow plants to bear fruits before 3rd year (since bud or graft saplings are coming there can be early flowering or premature fruit bearing phenomenon can happen. In such cases cut the flowers, so that tree saplings will yield sufficient vegetative growth before the flowering and fruit bearing). Once the tree achieved sufficient vegetative growth, give fertilizers with more Phosphorus proportion. Once the flowers start blooming, give micronutrients to avoid falling of flowers and better fruit bearing.
During vegetative growth we can keep plants in shade if needed. But once the plants start flowering, plants must be in direct sunlight. During its initial growth phase give