Expected standard size by end of week 4?

Transplant them into decent sized pots, those tiny cups are dreadfully under sized for proper root development and only really adequate for the first 5-7 days of growth. Pots about 4 inches across and 5 inches deep are far more suitable and have enough room and volume for great root growth and enough space for 3 weeks of development. You can't grow an elephant in a canary cage! You also need to start feeding them with proper grow nutrients, half strength to start with, the supplements you are now giving do not contain any major nutrients in any great concentration. Seaweed, silica and root stimulants will not provide your plant with the building blocks it needs to grow properly and they all lack adequate amounts of nitrogen, phosphorous and potassium (the major nutrients) that your plant needs to grow. At the moment, what you are giving is like feeding soup broth to a cage fighter, who really needs steak and carbs to perform to their best. Soup broth may prevent death, but will not provide the energy needed to perform at A level sports. It is all about nutrition and an adequate and balanced diet. Hope this helps, Organoman.