Wash and rinse pint canning jars; keep hot until ready to use. Prepare lids according to manufacturer's directions.
Place pickling spice on a clean, double-layered, 6-inch-square piece of 100% cheesecloth. Bring corners together and tie with a clean string. (Or use a purchased muslin spice bag).
Wash and peel tomatoes (place washed tomatoes in boiling water for 1 minute, immediately place in cold water, and slip off skins). Chop into ½-inch pieces. Peel, wash and dice onions into ¼-inch pieces. Wash, core, and seed bell peppers; chop into ¼-inch pieces. Combine chopped tomatoes, onions and peppers in an 8- or 10- quart Dutch oven or saucepot.
Wash, peel and pit peaches; cut into halves and soak for 10 minutes in an ascorbic acid solution (1500 mg in half gallon water). Wash, peel and core apples; cut into halves and soak for 10 minutes in ascorbic acid solution. Quickly chop peaches and apples into ½-inch cubes to prevent browning. Add chopped peaches and apples to the saucepot with the vegetables.
Add the pickling spice bag to the saucepot; stir in the salt, red pepper flakes, brown sugar and vinegar. Bring to boiling, stirring gently to mix ingredients. Reduce heat and simmer 30 minutes, stirring occasionally. Remove spice bag from pan and discard.
With a slotted spoon, fill salsa solids into hot, clean pint jars, leaving 1¼-inch headspace (about ¾ pound solids in each jar). Cover with cooking liquid, leaving ½-inch headspace.
Remove air bubbles and adjust headspace if needed. Wipe rims of jars with a dampened, clean paper towel; apply two-piece metal canning lids.
Process in a boiling water canner for 15 minutes. Let cool, undisturbed, 12 to 24 hours and check for seals.