The tips of my fairy castle cactus are turning brown?

Ive had it probably 3+ years, and just recently re-potted it maybe a month and a half ago. I watered it right after I planted it, then again 3 weeks later with half strength fertilizer. What could be wrong? Also today I let it get rained on by accident, the soil is quite saturated...should I re-pot in dry soil? And yes it is cactus/succulent soil. Thanks