The Loquat or Eriobotrya japonica is a small evergreen tree that can handle cold weather but nothing below 10 degrees...so if your new plant was not acclimated to the outdoors it may be suffering from exposure to cold spring night temps. Yellow leaves can also mean a plant not used to heat and so if you live in a very warm climate the plant may be suffering from heat stress. The brown tips on the leaves along with yellow could also be a sign of fertilizer burn, the soil drying out or even somebody tossing a cocktail into the soil. You may never know for sure what caused the distress but do not fertilize at this time, keep the soil moist and wait until you see signs of new growth before feeding with a slow release plant food such as Osmocote. Hard to say how often to water as it depends on your soil or climate so poke your finger into the soil and water when the top two inches is dry. May you have some lovely fruit in your future. Keep growing, Marianne Binetti