First of all, don’t panic. It is fairly common for both center and accent diamonds and gemstones to eventually need to have their prongs tightened. There are times you may even need to replace the prongs to ensure your gemstones don't become loose or fall out.
What you are experiencing is perfectly normal. Our bodies are constantly undergoing slight changes throughout the day, and as a rule, our fingers and toes tend to swell towards the end of each day. Therefore it is best to measure your ring finger at the end of the day when your finger is likely to be at its largest.
When caring for your pearls, the best thing to remember is "Last on and first off". Put your pearls on last, after you have applied any perfume, make-up, and sprays. First off - remove your pearls before pulling clothing over your head or washing your face. Cosmetics, sun block, perfume, and hair spray contain chemicals that can drastically dull the luster of a pearl.