properly pH pen calibrating ? how often ? and what is pH perfect doing ( i have pH up

Think you have 10-20 £ version on Amazon, or same for 3-5 on Chinese Alibaba. They dont last long or even come already faulty. Use all 3 . Yes, you can buy distilled water easy. Normal pens recomended to recalibrate every month. Perfect ph for soil 6.3 For coco veg 5.8-6.0 for coco flower 6.0-6.2 Buy KCL solution , put few drops every week into sponge of cap ( if there is no , take washing sponge, cut part and make one) probe should never dry I always had small range aquarium drops to double check. I use those, find alternative https://www.ebay.co.uk/itm/334219748618?hash=item4dd10ca50a:g:eUUAAOSwFIlhkjfa&amdata=enc%3AAQAIAAAA4LgHFRkOq1V5zBSwDZ4VBc%2Fsi90%2FqW2YSE4C9KOElH94rQe0xXS6xn%2F4BhxNXuzvZGv0ZZCBVNxNE0e6EMBxttWSOaAT3eo1wbG2mETKlL8nOjY0H%2FrJONrFfRdLB4tG5fNRjgkEq04B1N%2FU%2Bq0c6WVEjCaB%2FUqePSpAi18mHdPbsgVI%2B%2FK3Gn6qkZ0Is%2BMhGX2yG7zahguJGE%2FtD21jWPsh4PwfgUMY4lXNnU37P3xuadN93rxO020lQJBZrFPZXE9EACEGkzasMW5FnfajsDGZk6gKkPphf6UZG8AZY8Uk%7Ctkp%3ABk9SR-LR4dXGYg And rethink , maybe you need normal long lasting pen. Check BlueLab, running costs a bit expensive ( for kcl or calibration solutions 4.0 and 7.0 ) Kcl is Potassium chloride